Piston-type accumulators are provided with a large number of designs. The part of the piston housing, surrounding the separating piston and extending axially, is in the form of a cylindrical tube. For this reason, the piston-type accumulator is often also termed a cylindrical accumulator. The sealing areas on the circumference of the separating piston customarily are formed of annular or O-ring seals which are seated in external circumferential grooves axially offset from each other in the separating piston.
Very high requirements are set, such as that of operation over wide temperature ranges, for example, between −40° C. and 150° C., from the viewpoint of the operating capacity of such cylindrical or piston-type accumulators. Test stand experiments show that accumulators do not function satisfactorily with respect to long-term behavior, since gas often overflows toward the oil or fluid side. Such behavior is not acceptable in the case of accumulators which are to perform a safety function, especially if the accumulators involved are used in conjunction with hydraulic braking systems. Overflow of gas into the hydraulic braking system could result in malfunction or even failure.